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cultiv8 writes "A research team from Seoul National University (SNU) said the genetically modified female beagle has been found to glow fluorescent green under ultraviolet light if given a doxycycline antibiotic. The researchers, who completed a two-year test, said the ability to glow can be turned on or off by adding a drug to the dog's food. 'The creation of Tegon opens new horizons since the gene injected to make the dog glow can be substituted with genes that trigger fatal human diseases,' the news agency quoted lead researcher Lee Byeong-chun as saying. He said the dog was created using the somatic cell nuclear transfer technology that the university team used to make the world's first cloned dog, Snuppy, in 2005."

While I don't mean to belittle the work done by these scientists, I want to point out a common mistake used in science journalism - referring to GFP as "glowing". It does not glow, in any sense of the word. It fluoresces, which means you need to shine blue or UV light on it and examine it through a filter that removes the incident light, and then it will appear green. It can appear quite amazing under those conditions, but you can't take this dog out for a walk at night and see it emitting green light. You won't even see it reflecting green light, unless you take him near a UV source.

It's a quick and dirty way to test whether the inserted gene is being expressed in all tissues.

Step two is to attach your desired test gene to the bioluminescent gene. Now you can see where the test gene is being expressed. That removes the doubt from a failure to get the expected result; is it because the experimental treatment doesn't work properly, or because the gene isn't active in the desired tissue? Failure+glow means the treatment failed. Failure+no-glow means a problem with the insertion.

IAAB. It's equivalent to using a print statement as a report mechanism during debugging. In fact, this use of GFP is even called a "reporter" gene. There are other reporters commonly used; prior to the discovery of fluorescent proteins, the most popular bacterial reporter was a step in the lactose metabolism pathway that caused the colony to turn blue when it was interrupted by another gene (thus demonstrating not functionality, but that the gene had been inserted correctly into the carrier molecule.)

Another control mechanism that's often used is antibiotic resistance: if it doesn't die, then the resistance gene is where it should be. This has the added benefit of getting rid of the samples you don't want at the same time. Of course, neither of these are very useful for seeing tissue-specific expression, which is why fluorescent proteins revolutionized molecular biology when they were discovered.